Solar well control [RE-wrenches]

Matt Tritt solarone at charter.net
Fri Dec 21 09:26:41 PST 2007


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OK, OK, I may be crazy, but who /else /is going to work so hard for such 
little money?

I agree with Windy that the SunPumps are very good in their application 
rage, but I also know about certain "eccentricities" with these babies 
that make me remind everyone not to attempt taking them apart (the wet 
end) after they've been in service. Carramba! A friend of mine just 
about lost his face while attempting a field repair on one out on Santa 
Cruz island because of the incredible internal pressure that has no 
where to go until you loosen the screws. Windy?

And yep; Hudson valves are good and very reliable. They're used in snow 
country, but I've never heard of one failing except because of some bull 
attempting plumbing repairs without the proper tools.

I also wouldn't forget to mention that the SQ D pressure switches need 
to be carefully sealed with silicone to prevent ants and/or earwigs from 
getting in and crowding between the contacts. In the time I've been 
doing pumps, I bet that 25% of nuisance calls I've had have been from 
bugs getting crushed between the contacts and preventing pumps from 
shutting off. Ugh.

Matt

Windy Dankoff wrote:

>
> William,
>
> Hear Ye All Wrenches -- Matt Tritt is STILL selling solar water pumps  
> after all these years, so DO WHAT HE SAYS. HE'S CRAZY!
>
> I agree with using a "toggle"-action (positive shutoff) float valve  
> and a small pressure tank to eliminate on/off chatter. As long as the  
> pump has the reserve lift capacity to hand the brief increase in  
> pressure to shut off. I've recommended this many times. There's an  
> inexpensive valve called Hudson Valve that is commonly used for 
> animal  watering -- $25. I tested one once, and then recommended it 
> to  numerous people and never got back any bad reports. Search it and  
> you'll find what you need to know. Matt or Jeff? Ever try one?
>
> With all respect to Matt, If diaphragm pumps are the bottom of the  
> line, then SunPumps is the TOP of the bottom. Their Quad has been  
> especially good for many years, in part cuz it's limited to about 100  
> feet and all the diaphragm pumps have done MUCH better in that lower  
> lift range, including Shurflo. Certainly, for low water needs they 
> may  be worth considering.
>
> So yes William, your logic is perfect. I've used standard Square-D  
> pressure switches and been able to adjust them down to about 15 PSI  
> shutoff, or maybe lower, I don't remember. Below that, they get  
> sloppy. Set the pre-charge in the pressure tank to roughly half of 
> the  cut-out pressure. It doesn't seem to matter much what it is, but 
> if  you get an on/off chatter (water hammer) at the P switch, 
> re-adjust  the pre-charge pressure.
>
> Normally, you would run the P switch to a low-level control circuit 
> on  the SunPumps controller, so arcing won't happen.
>
> But just cuz I have nothing better to do, I'll advise on switching DC  
> directly:
>
> Regarding mechanical contacts on switches, relays, etc. if they have  
> both DC and AC ratings, you will always (far as I've known) see that  
> the amp rating at 32VDC is equal to the amp rating at 125VAC. The 
> only  exception I've seen to that is directly in the PV array circuit, 
> where  the voltage, when it breaks, rises far higher and may sustain 
> an arc.  On the Square-D P switches, I remember not seeing a DC rating 
> on the  switch cover, but seeing it in the catalog listing.
>
> Be sure to use both sets of contacts. That will suppress any arcing.  
> If the system is negative grounded (not necessary or advisable on a  
> stand-along solar pump),  you should break only the positive side, 
> per  code. In that case, run it through BOTH sets of contacts IN 
> SERIES.  Whether you do this or break both + and -, it's the same 
> effect. Any  arc would have two jump through two gaps in series.
>
> My two dull pennies.
> Windy
>
>
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